You may sacrifice the Herald itself to help pay for the cost of its ability.
, , Sacrifice a blue creature, a black creature, and a red creature: Search your library for a card named Prince of Thralls, put it onto the battlefield, then shuffle.
To activate the ability, you must sacrifice three different creatures. You can’t sacrifice just one three-colored creature, for example.
You may sacrifice multicolored creatures as part of the cost of the search ability. If you sacrifice a multicolored creature this way, specify which part of the cost that creature is satisfying.
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